[Methylmalonic aciduria associated with myoclonic convulsions, psychomotor retardation and hypsarrhythmia]

Organic acidurias have long been known to cause neurological problems, such as convulsions, stupor, coma, and psychomotor and mental retardation. The organic acidurias include propionic aciduria, methylmalonic aciduria (MMA), isovaleric acidemia, lactic acidemia and glutaric acidemia type I. However, the association of MMA with electrical activity of the brain characterised by a hypsarrhythmic pattern, refractory convulsions and psychomotor retardation is very rare.

Two patients, one male and one female, were seen to have psychomotor retardation, erratic attacks of myoclonic convulsions, hypsarrhythmic encephalographic pattern and an increase in the urinary excretion of methylmalonic acid, as shown by gas chromatography and mass spectrometry, all of which supported a diagnosis of MMA in both cases. In one patient, the brain MRI with gadolinium showed lesions compatible with brain atrophy. Protein restrictions, the administration of vitamin B12 and l carnitine re established the normal neurological state and reduced the urinary excretion of methylmalonic acid in one of them.

To the best of our knowledge these are the first cases of MMA that have been seen accompanied by hypsarrhythmia. The rareness of this clinical presentation with the characteristics described above make us suspect that we are dealing with a new clinical syndrome.